If I guess right, you have something like this:
The colored lines are the actual drawing and the black ones are help lines towards a vanishing point. You have got drawing 1, you want drawing 3, but scaling + holding shift makes 2.
You do not want simply scale everything, because there's also something else in the drawing which is not shown here. The help lines + the unshown part must stay intact.
You can get 3. Keep the actual drawing in different layer than the help lines or lock the help lines. Learn to make selections and lockings via the layers panel.
See the green line. Its only my vanishing point marker in the actual drawing. I select all parts of the drawing that I want to scale, also the marker. Then I scale(holding shift or with Transform > Scale). I drag the top node of the marker with the direct selection tool to the vanishing point, the rest follows (see NOTE1) and everything is perfect again.
Do the same. Have snap to points and smart guides =ON, no other snaps!
NOTE1: Beware clicking anything between the scaling and dragging the marker node. If that happens, you must deselect all, select again and do the drag. Otherwise only the top node of the marker moves.
Add due a comment:
Seemingly I quessed wrong. You seem to be trying to make in the fly new bricks to be laid to a perspective image.
It would be far easier to lay a full rectangular straight view of a wall using equal bricks and then apply perspective transform to it. Simply drag a rectangular image with the perspective selection tool to the perspective grid. Keep a rectangular copy, too just in case you want to change the perspective later.
Rectangular shapes can even be extruded +rendered in Illustrator with a perspective and texture images (=placed symbols) on their surfaces. See an example